Most semiconductor laser diodes available nowadays are double-heterostructure laser diodes. The manufacture of these heterostructure diodes is simpler and, thus, better understood when it is compared to the more complex quantum-well laser diodes. It also guarantees higher yields.
The present invention relates to an improved heterostructure diode that only requires slight modifications to an existing manufacturing process, This is clearly preferable to starting a new manufacturing process and accepting risks of unknown reliability. Prior to switching from a conventional double-heterostructure laser diode to a quantum well laser diode, the intermediate step towards an improved heterostructure diode is deemed to be adequate for most manufacturers.
Single-Heterostructure diodes (SH) and Double-Heterostructure diodes (DH) will, henceforth, be addressed independently of their material, structure, and layer configuration. Details on Single-Heterostructure and Double-Heterostructure laser diodes and light emitting diodes are provided in Chapter 12, 'LED and Semiconductor Lasers' in the book "Physics of Semiconductor Devices", S. M. Sze, Second Edition, John Wiley & Sons, New York, 1981.